A common automobile heat exchanger is configured, as shown in FIG. 4, so that a heat radiation fin 112 processed like a corrugation is integrally formed between planular tubes 111 provided plurally like a radiator 100 and so that both ends of the tubes 111 are respectively opened to a space configured with a header 113 and a tank (not shown).
The radiator 100 of such the configuration sends a refrigerant of a high temperature from a space of one tank to that of the other tank through each inside of the tubes 111 and again circulates the refrigerant that becomes a lower temperature by exchanging heat between the tubes 111 and the heat radiation fin 112.
In the tubes 111, as shown in FIG. 4, cladding one side of a core material 102 with a skin material (also called a sacrificial electrode material) 103, forming an aluminum alloy brazing sheet 101 (see FIG. 5), where the other side of the core material 102 is clad with a brazing material 104, like a planular tube by such a forming roll, and performing electric resistance welding or heating and brazing, whereby the aluminum alloy brazing sheet 101 itself is brazed and liquid paths of the tubes 111 are formed.
Meanwhile, in the core material 102 is used an Al—Mn series alloy such as alloy No. 3003 specified in JIS H 4000 from a view point of an anticorrosion and a strength; in the skin material 103 always contacting a refrigerant are used alloy No. 7072, and Al—Zn series and an Al—Zn—Mg series alloy such as Al-2 to 5% Zn-2 to 4% Mg, and in the brazing material 104 is used an Al—Si series alloy such as alloy No. 4045 of a lower melting point.
The radiator 100 is integrally assembled by brazing, using the tubes 111 configured above, the radiation fin 112 where corrugated processing is performed, and other members. As a brazing method can be cited such a flux brazing method and a Nocolok brazing method of using a noncorrosive flux; and brazing is performed, heating the members described above at a high temperature of approximately 600 degrees Celsius.
In the radiator 100 thus assembled, specifically in the tubes 111, a refrigerant of a high temperature to a low temperature and a high pressure to a normal pressure results in always passing and circulating. In other words, because a repetitive stress is loaded to the tubes 111, a fatigue characteristic for enduring this is requested.
It is generally known that the fatigue characteristic relates to a static tensile strength, and a material where Cu is added is proposed in order to improve the tensile strength of a raw material also in a heat exchanger (for example, see Japanese Patent Laid-Open Publication No. H10-53827 (claims 1 to 4 and paragraph 0013).